The present invention relates to a combined support and end cover structure for electric motors, and in particular for low power dc motors of the type having pole pieces embodied as permanent magnets. In current methods of manufacturing dc motors, the external and internal structural parts housing and supporting the assembly of stator, rotor, rotor shaft, commutator and brushgear are embodied as a central frame, to the internal surface of which the stator pole pieces and their relative exciting windings are mounted, symmetrically arranged and spaced apart at regular angular distances, and a pair of covers at front and rear, the centers of which incorporate brackets for the rotor shaft bearings.
The bearing bracket of the cover at the commutator side of the motor affords an inward facing collar over which to -it the hub of a spider mounting that provides a rigid support for the stems carrying the brush holders.
In the particular instance of small dc electric motors, there is no bracket on the cover at the commutator side to support a brushgear spider and collar arrangement of the type mentioned; instead, the cover affords a hole to accommodate the end of the rotor shaft and the brushes are mounted direct to the internal face of the cover, radiating from the hole and supported by relative guides generally fashioned in metal, whilst the external surface is fitted with a cap disposed coaxially with the hole accommodating the shaft and containing a journal bearing for the projecting end of the shaft. Likewise in the case of permanent magnet type dc motors, the pole pieces are fitted conventionally to the internal surface of the central fame in the manner mentioned above.
The shaft extension is located at the end of the frame opposite to that occupied by the brushgear, and accordingly, this end is fitted with a second cover, similar to the first and provided with a central bracket to support the shaft.
The main drawback besetting construction methods as outlined above is that of the considerable number of single components which combine to make up the external and internal structure accommodating and supporting the working parts of the electric motor, which in turn renders it impossible to contain the longitudinal dimension of the assembled unit. Excessive length in a small dc motor tends to impose notable limitations on its use, especially with regard to automotive applications in which certain types of unit are required to drive parts located in cramped spaces, for example booster fans and electric windows.
An additional drawback stems from the fact that with a considerable number of single components combining to make up the external and internal structure accommodating and supporting the working parts of the electric motor, assembly operations become relatively lengthy, and the resultant loss of time is reflected in the purchase price of the end-product.
Accordingly, the object of the present invention is to overcome the drawbacks mentioned above.